The motor was not open for any length of time....only when working on it.

Nothing was dropped in there, as far as I know. No missing parts, clips, etc. Everything is accounted for.

There was coolant in bike. heat cycled, as as I did on the other rebuilds. Only other thing than the previous, those were done in heat of summer, and this was during colder, more recent weather.

Basically, I did nothing different than I did on previous top end rebuilds. Makes it that much more baffling.

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Hey old pal,,,,did you flush the cases totaly before you put it together.
That was something caught between the piston/rings and clynder.:huh
I had a bike years ago,that i had someone else rebuild.And after couple hundred miles i heard a bad,bad noise.
Pulled it apart and it looked like someone went to town with a diegrinder.
Come to find out the fucktard dropped a circlip in the case while putting one of the pistons in,and instead of spliting the cases to fish it out,,he just got another and put the motor together.
The pistons looked just like that.Took awhile to figure it out,cause i had all the parts it was supposed to have.
Just say'n.

@ John: Wiseco piston. Ill have to pull plug and look at it again. O did pull it to see if it was white....indicating a lean condition. It was dark...IIRC.

@ Scott : the bottom end was totally redone by Andrew Cooksey when I redid bike. He does great work and bottom end came back like new. I did top end and installed in bike. I had about 20 hrs on that topend but then developed a lean condition that I was chasing after tuning it one day. I had gotten a big airleak and was thinking it was the base gasket ..so I decidedif to change it. Other than running lean, mechanically, it was strong and ran well.

Consensus is something got stuck in there between piston and wall

..but what remains to be seen.

Bike is maxed out on worth vs what I have in it. So now, my issue is do I put the money it needs to run right again ...$400- 500 more????

Hey guys. I may want to freshen up the plastic on my '09.
Where are you guys getting plastic? OEM? Can I get something other than the stock orange for an '09?
How about graphics? Who are you buying from?

I was going to put an SX head on my '11 300 XC-W. The higher compression is supposed to boost low end torque, especially at our high altitude.

I was chatting with a guy on the trail this weekend who had done the mod. His already miserable gas mileage got worse. This might dissuade me.

Anyone else have experience on gas mileage differences? I've finally got my jetting sorted out, and I'm still disappointed with the mileage. I'm not sure the additional torque would be worth the decreased range.

Hey guys. I may want to freshen up the plastic on my '09.
Where are you guys getting plastic? OEM? Can I get something other than the stock orange for an '09?
How about graphics? Who are you buying from?

Thanks!

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Acerbis makes aftermarket in multiple colors. They should be available from the major mail order places.

I was going to put an SX head on my '11 300 XC-W. The higher compression is supposed to boost low end torque, especially at our high altitude.

I was chatting with a guy on the trail this weekend who had done the mod. His already miserable gas mileage got worse. This might dissuade me.

Anyone else have experience on gas mileage differences? I've finally got my jetting sorted out, and I'm still disappointed with the mileage. I'm not sure the additional torque would be worth the decreased range.

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I get around 32+ MPG in average dirt. It may go a little less in WFO desert sand, but not a whole lot less. I think that is great.
Stock head, JD jetting, gnarly pipe.

Just a head's up for anyone interested. I am going to be selling my 98 KTM 300 EXC...as seen in posts in this thread. Needs new top end/replated cylinder. That is the bad, the good is its a legally plated two stroke in NJ.

Reason: Just had a kid, and have no time to ride, not to mention time to fix this, nor the money....so I shall part ways with it, to someone that can use it, instead of it rotting to death in my shed.

Full disclosure about bike can be seen in all my posting in this thread.

I have a tentative offer from riding buddy of a riding buddy. If that falls through, I will be putting it up on here first...and will link my flea market thread.